Thermal copying machine

ABSTRACT

Exposure control is achieved in a simplified thermographic copy machine by adjusting the spacing of the radiation source with respect to the print roll while maintaining constant speed and constant radiation output.

[451 Jan. 18,1972

References Cited [54] THERMAL COPYING MACHINE [72] Inventor: Harlan L.Krlnke, May Township, UNITED STATES PATENTS Washington County, Minn.

[73] Assignee: Minnesota Mining and Mnnulacmrlng d a u y m h u K W. 9 H6 5 6 1 In 9 n. 2

2,987,603 6/1961 Thomson............ 3,150,262 9/l964Ulsetheta]..........................

Company, St. Paul, Minn.

Mar. 2, 1970 Primary Examiner-Anthony L. Birch [22] Filed:

Attomey-Kinney, Alexander, Sell, Steldt & Delahunt [21] Appi. No.2

Aas'nmc'r Exposure control is achieved in a simplified thermographiccopy machine by adjusting the spacing of the radiation source withrespect to the print roll while maintainin and constant radiationoutput.

g constant speed 10 Claims, 6 Drawing Figures PATENTED JAN 1 8 9 2THERMAL COPYING MACHINE This invention relates to the thermographiccopying of differentially radiation-absorptive graphic originalsand inparticular to novel copying apparatus used therein.

A form of thermographic copying machine which has achieved widespreadpopularity is shown in US. Pat. No. 2,891,165. In the machine theredescribed, the original and heat-sensitive copy sheet are carried on atransparent belt past a print roll where they are briefly incrementallyexposedto intense radiant energy from a line filament lamp supported ina focusing reflector which concentrates the radiation along a narrowline at the surface of the original. Variations inexposure, whenrequired to compensate for changes in ambient temperature, differenttypes and arrangements 'of sheet materials, or other variables, areachieved by varying the speed of travel of the carrier. Thus the timerequired to make a given number of copies may vary.

The-device of the present invention employs a different and simplifiedform of control and makes possible thepreparation of copies at constantrate. The simplified constructionpermits significant weight reductionand providesfor areadily portable machine.

A .presently preferred form of apparatus embodying the principles of theinvention in a portable model is illustrated in the accompanyingdrawing, wherein FIG. I is a view in perspective of the portable thermalcopying device in position for transporting;

P16. 2 is a-schematic illustration showing the drive,.irradiation, andpaper-carrying components of the device largely in cross section, and

FlG. 3 is a schematic illustration of components of FlG.2 in partiallycutaway elevation;

FIG. 4 is a detail view schematically illustrating a form of controllinkage; and

FIGS. 5 and 6 show schematically in partial planand elevational viewsfurther'details of an optional automatic control assembly.

The copy machine 10 is contained within a case having an extendedgenerally triangularly cross-sectioned handle member 12. An input slot13 is provided in the top'panel 14 along one edge of the handle; anoutput slot 13 'is similarly provided along the opposite edge. Anon-off'button [Sand a control button 16 occupy positions on'the inputface of the handle. A louvered ventilation opening 17 is provided on oneend as shown; a similar opening, not-shown, occupies the opposite .end.A receptacle l8 permits connection to be made to an electric plug andcord. The handle 12 is' provided with a handhole 19 forconvenience incarryingthe machine.

Within the case and supported on suitable frame members, not shown, areprint roller 21, drive roller- 22, belt guide roller 23, idler roller24, tension roller 25,.and motor'drive unit26. The belt guide roller isdesirably as described in'U'.S. Pat. No. 3,149,497. A transparentheat-resistance belt/.27 encircles' the rollers as shown. A radiationsource unit28 adjacentthe print roll provides the requiredhigh-intensity radiation. Thedrive unit is connected to the drive rollerthrougha drive belt 29 and carries a cooling fan 30.

The source unit 28 comprises an elongate coiled tungsten filament lamp31 supported at one focus of a troughlike'elliptically cross-sectionedpartial reflector 32. The reflector is supported between end plates 33,34 which are pivotally supported from the frame,'the pivot 35beingindicated'for plate 34 inFlG. 4. The opposite end'of plate 34ispivotally supported, by pivot pin 36, from a lever 37 pivotallyattachedto the frame atpivot 38and to a'bar 39 at pivot 40. The'bar 39terminates in control button 16. Sliding movement of thecontrol buttonthus pivotally positions the source unit at any desired location, fromcontact with the belt 27 to some significant distance therefrom. Exactpositioning may be estimated from a suitable scale 41 provided for thepurposeon .the-surface of the handle 12.

in use as a copying machine, the device is laidonitsside with the inputslot 13 upwards and is connected to asuitable source of power. Thecomposite of. graphic original and heattion of the original on the copysheet.

' The extent of the heating effect achieved at'the image areas,

.and therefore the accuracy of reproduction, is controlled by thepositioning of the control button 16. Maximum utilization of radiationis achieved with the button in full forward position and with the edgesof the reflector substantially in contact with the belt. As thereflector is gradually withdrawn from such position, increasingproportions of the radiation are lost from the print zoneand the heatingeffect is lessened. The adjustment makes possible the successful copyingof a variety of originals on a variety of copy sheets, at a constantrate.

The pivotal movement of the source unit is sufficient to displace theline of focus of the reflector a significant distance from the surfaceof the graphic original. Surprisingly, it is found that accuratefocusing, to provide the narrowest possible line of intense radiantenergyiis not essential to the successful operation of the device. Theintensity of the broadened band of radiation is found to be entirelyadequate to provide the required increase in temperature at theradiation-absorptive image areas; and the time of irradiation remainssufficient'ly brief to avoid any significant lateral spread of the heatpattern. The lamp is operated at fixed power inputand hence at fixedradiation output; no current control devices are required. Heat buildupwithin the machine is held to a minimum, as contrasted with systemswherein movable shutters control the proportion of radiation reachingthe print zone by retaining the radiation within the reflector.

Some of the radiation escaping from the source unit through the openspaces adjacent the edges 'of the reflector may strike the original butat such a low. angle as to have substantially no heating efi'ect. Mostof the escaping-radiation will be directed tangentially of the printroller. While the radiation not reaching'the print zone may be absorbedin other machine components, the heating effect is compensated for bythe continuous movement of air obtained with the constant-speed fan Thepivot pin 36 operates within an elongate narrow slot in the lever 37 tocompensate for'the opposing arcs of the lever and the frame 34. in asimplified construction the pin is attached directly toend plate 34 asindicated inFlG. 4, and any adjustment required by change in ambient ormachine temperature must then be made through the button 16. lnv aexpansion than does'the reflector shell 32, so that as the temperatureofthe system is increased the pin 16' is moved in a direction tending'tocause increased loss of radiation at the print zone. Initial adjustmentof the control linkage may be accomplished by altering the positions'ofthe rods 53, 55 through screw adjustments adjacent the supporting:plates 33, 34. Spring 56 or equivalent biasing means maybe added toovercome any lost motion in the control linkage.

Pressure applied to the button 15 actuates a switch which simultaneouslystarts the motor unit 26 and turns on the lamp 31. After the copy hasbeen finished and ejected, releasing the button extinguishes the lamp;but the motor continues to run until the device has cooled sufficientlyas controlled by a thermostat.

What is claimed is as'follows:

l. A .thermographic copy-machine wherein a composite of graphic originaland heat-sensitive copy sheet is incrementally briefly exposed within aprint zone to intense radiant energy from a line source of energycomprising means for operation at constant uniform speed and constantuniform radiation output, and exposure control means for permitting adesired proportion of said radiation output to be directed away fromsaid print zone along the entire said source.

2. The copy machine of claim 1 including a print roller and atransparent heat-resistant belt for incrementally advancing a saidcomposite, and wherein said line source includes a troughlike reflectorfor directing said radiation toward said print zone, and said controlmeans includes means for positioning said reflector to permit saidproportion of radiation to be directed away from said print zone.

3. The copy machine of claim 2 wherein said reflector is mounted forpivotal movement toward or away from said print zone.

4. The copy machine of claim 2 wherein said troughlike reflector has atruncated elliptical cross section and the source of radiation isdisposed along a focus thereof.

5. A constant-speed thennographic copy machine comprising a printroller, a transparent heat-resistant carrier contacting said printroller to provide a print zone, means for driving said carrier and printroller so as to advance a composite of graphic original andheat-sensitive copy sheet therebetween and through said print zone,radiation source means including a line source of radiation adjacentsaid print zone and a reflector for directing the radiation from saidsource to said print zone, and control means for permitting escape ofany desired proportion of said radiation along the entire length of saidradiation source means in a direction away from said print zone.

6. The copy machine of claim 5 wherein said reflector is mounted forpivotal movement toward or away from said control zone and includingpivoting means for providing said movement.

7. The copy machine of claim 6 wherein said pivoting means includesinternal differential expansion thermostat means for pivoting saidreflector away from said control zone as the temperature of saidreflector increases.

8. The copy machine of claim 6 wherein said pivoting means includesexternal handle means and interconnecting linkage means for permittingmanual pivotal movement of said reflect0).

9. The copy machine of claim 7 wherein said reflector serves as one ofthe difi'erential expansion components of said thermostat.

10. The method of operating a therrnographic copy machine, having meansfor incrementally briefly exposing a composite of graphic original andheat-sensitive copy sheet to intense radiation, for effective copyingunder all appropriate conditions, comprising operating said machineat'fixed copying speed and fixed radiation output rate, and adjustingthe proportion of said radiation utilized, in exposing said composite,to the level required for effective copying, by permitting escape of theremaining proportion in a direction away from the incremental exposurearea.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORREC'NON 2 'Patent No. 3, 35 Dated January 18, 197

I ven Harlan L Kr inke It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

001. 1, line +1 "13" should be "13'" Signed and sealed this 18th day ofJuly 1972.

(SEAL) Attest:

EDWARD M.F'IETCHER,JR. ROBERT GOI'TSCHALK Attesting Officer Commissionerof Patents i FORM (10-69) USCOMM-DC scan-ps9 I U.S. GOVERNMENT PRINTINGOFFICE} '99 0-366-33

1. A thermographic copy machine wherein a composite of graphic originaland heat-sensitive copy sheet is incrementally briefly exposed within aprint zone to intense radiant energy from a line source of energycomprising means for operation at constant uniform speed and constantuniform radiation output, and exposure control means for permitting adesired proportion of said radiation output to be directed away fromsaid print zone along the entire said source.
 2. The copy machine ofclaim 1 including a print roller and a transparent heat-resistant beltfor incrementally advancing a said composite, and wherein said linesource includes a troughlike reflector for directing said radiationtoward said print zone, and said control means includes means forpositioning said reflector to permit said proportion of radiation to bedirected away from said print zone.
 3. The copy machine of claim 2wherein said reflector is mounted for pivotal movement toward or awayfrom said print zone.
 4. The copy machine of claim 2 wherein saidtroughlike reflector has a truncated elliptical cross section and thesource of radiation is disposed along a focus thereof.
 5. Aconstant-speed thermographic copy machine comprising a print roller, atransparent heat-resistant carrier contacting said print roller toprovide a print zone, means for driving said carrier and print roller soas to advance a composite of graphic original and heat-sensitive copysheet therebetween and through said print zone, radiation source meansincluding a line source of radiation adjacent said print zone and areflector for directing the radiation from said source to said printzone, and control means for permitting escape of any desired proportionof said radiation along the entire length of said radiation source meansin a direction away from said print zone.
 6. The copy machine of claim 5wherein said reflector is mounted for pivotal movement toward or awayfrom said control zone and including pivoting means for providing saidmovement.
 7. The copy machine of claim 6 wherein said pivoting meansincludes internal differential expansion thermostat means for pivotingsaid reflector away from said control zone as the temperature of saidreflector increases.
 8. The copy machine of claim 6 wherein saidpivoting means includes external handle means and interconnectinglinkage means for permitting manual pivotal movement of said reflector.9. The copy machine of claim 7 wherein said reflector serves as one ofthe differential expansion components of said thermostat.
 10. The methodof operating a thermographic copy machine, having means forincrementally briefly exposing a composite of graphic original andheat-sensitive copy sheet to intense radiation, for effective copyingunder all appropriate conditions, comprising operating said machine atfixed copying speed and fixed radiation output rate, and adjusting thepropoRtion of said radiation utilized in exposing said composite, to thelevel required for effective copying, by permitting escape of theremaining proportion in a direction away from the incremental exposurearea.